Regeneration of a coke deactivated catalyst comprising a combination of platinum rhenium and halogen with a porous carrier material

ABSTRACT

A DEACTIVATED HYDROCARBON CONVERSION CATALYST, WHICH IS A COMBINATION OF A PLATINUM GROUP COMPONENT, A RHENIUM COMPONENT AND A HALOGEN COMPONENT WITH A POROUS CARRIER MATERIAL AND WHICH HAS BENN DEACTIVATED BY DEPOSITION OF CARBONACEOUS MATERIAL THEREON DURING A PREVIOUS CONTACTING WITH A HYDROCARBON CHARGE STOCK AT AN ELEVATED TEMPERATURE, IS REGENERATED BY THE SEQUEENTIAL STEPS OF:(1E) BURNING CARBON THEREFRROM AT A RELATIVELY LOW TEMPERATURE WITH A GAS STREAM CONTAINING HALOGEN OR A HALOGEN-CONTAINING COMPOUND, H2O, AND A RELATIVELY SMALL AMOUNT OF 32, (2) TREATING THE RESULTING PARTIALLY REGENERATED CATLYST AT A RELATIVELY HIGHER TEMPERATURE WITH A GAS STREAM CONTAINING A HALOGEN OR A HALOGENCONTAINING COMPOUND, H2O, AND A RELATIVELY HIGHER AMOUNT OF O2, (3) PURGING O2 AND H2OO FROM CONTACT WITH THE RESULTING CATALYST, AND, (4) SUBJECTING THE RESULTING CATALYST TO CONTACT WITH A DRY HYDROGEN STREAM. KEY FEATURES OF THE DISCLOSED METHOD ARE: (1) PRESENCE OF WATER AND HALOGEN IN THE GAS STREAM USED IN THE CARBON-BURNING STEP AND IN THE OXYGEN-TREATING STEP, (2) CAREFUL CONTROL OF THE TEMPERATURE DURING EACH STEP, (3) MAINTENCE OF THE HALOGEN CONTENT OF THE CATALYST AT A RELATIVELY HIGH LEVEL DURING THE ENTIRE REGENERATION PROCEDURE, AND (4) CAREFUL CONTROL OVER THE COMPOSITION OF THE GAS STREAMS USED IN THE VARIOUS STEPS THEREOF.

United States Patent 26 Claims ABSTRACT OF THE DISCLOSURE A deactivated hydrocarbon conversion catalyst, which is a combination of a platinum group component, a rhenium component, and a halogen component with a porous carrier material and which has been deactivated by deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature, is regenerated by the sequential steps of: 1) burning carbon therefrom at a relatively low temperature with a gas stream containing halogen or a halogen-containing compound, H 0, and a relatively small amount of O (2) treating the resulting partially regenerated catalyst at a relatively higher temperature with a gas stream containing a halogen or a halogencontaining compound, H 0, and a relatively higher amount of O (3) purging O and H 0 from contact with the resulting catalyst, and, (4) subjecting the resulting catalyst to contact with a dry hydrogen stream. Key features of the disclosed method are: (1) presence of water and halogen in the gas stream used in the carbon-burning step and in the oxygen-treating step, (2) careful control of the temperature during each step, (3) maintenance of the halogen content of the catalyst at a relatively high level during the entire regeneration procedure, and (4) careful control over the composition of the gas streams used in the various steps thereof.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of my prior, copending application Ser. No. 805,380, filed Mar. 7, 1969, now abandoned.

DISCLOSURE The subject of the present invention is a method for regenerating a coke-deactivated hydro carbon conversion catalyst comprising a platinum group component, a rhenium component, and a halogen component combined with a porous carrier material. More specifically, the present invention is a method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of platinum, rhenium and halogen with an alumina carrier material where the catalyst has been deactivated by the deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature. In essence, the present invention provides a specific sequence of carbon-burning and catalyst treatment steps designed to result in a regenerated catalyst possessing activity, selectivity, and stability characteristics which are comparable to those observed with the fresh undeactivated catalyst.

Composites having a hydrogenation-dehydrogenation function and a cracking function are widely used today as catalysts in many industries, such as the petroleum and petrochemical industry, to accelerate a wide spectrum of hydrocarbon conversion reactions. Generally, the cracking function is thought to be associated with an acidacting material of the porous, adsorptive, refractory oxide 3,753,926 Patented Aug. 21, 1973 type which is typically utilized as the support or carrier for a heavy metal component such as one or more of the metals or compounds of metals of Group V through VIII of the Periodic Table to which are generally attributed the hydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety of hydrocarbon conversion reactions such as hydrocracking, isomerization, dehydrogenation, hydrogenation, desulfurization, cyclization, alkylation, polymerization, cracking, hydroisomerization, etc. In many cases, the commercial applications of these catalysts are in processes where more than one of these reactions are proceeding simultaneously. As example of this type of process is reforming wherein a hydrocarbon feed stream containing parafiins and naphthenes, is subjected to conditions which promote dehydrogenation of naphthenes to aromatics, dehydrocyclization of paraflins to aromatics, isomerization of parafllns and naphthenes, hydrocracking of naphthenes and paraffins and the like reactions, to produce an octanerich or aromatic-rich product stream. Another example is a hydrocracking process wherein catalysts of this type are utilized to effect selective hydrogenation and cracking of high molecular weight unsaturated materials, selec tive hydrocracking of high molecular weight materials, and other like reactions, to produce a generally lower boiling, more valuable output stream. Yet another example is an isomerization process wherein a hydrocarbon fraction which is relatively rich in straight-chain paraflin components is contacted with a dual-function catalyst to produce an output stream rich in isoparaflin compounds.

Regardless of the reaction involved or the particular process involved, it is of critical importance that the dual-function catalyst exhibit not only the capability to initially perform the specified functions, but also that it has the capability to perform them satisfactorily for prolonged periods of time. The analytical terms used in the art to measure how well a particular catalyst performs its intended functions in a particular hydrocarbon reaction environment are activity, selectivity, and stability. And for purposes of discussion here, these terms are conveniently defined for a given charge stock as follows: (1) activity is a measure of the catalysts ability to convert hydrocarbon reactants into products at a specified severity level where severity level means the conditions usedthat is the temperature, pressure, contact time, and presence of diluents such as H (2) selectivity refers to the amount of the desired product and/or products obtained as a function of the amount of the reactants converted or charged; (3) stability refers to the rate of change with time of the activity and selectivity parameters-obviously the smaller rate implying the more stable catalyst. In a re forming process, for example activity commonly refers to the amount of conversion that takes place for a given charge stock at a specified severity level and is typically measured by octane number of the (35* product stream; selectivity refers to the amount of C yield that is obtained relative to the amount of charge at the particular severity level; and stability is typically equated to the rate of change with time of activity, as measured by octane number of C product, and of selectivity, as measured C yield. Actually, the last statement is not strictly correct because generally a continuous forming process is run to produce a constant octane C product with the severity level being continuously adjusted to attain this result; and, furthermore, the severity level is for this process usually varied by adjusting the conversion temperature, in the reaction zone so that, in point of fact, the rate of change of activity finds response in the rate of change of conversion temperature, and changes in this last parameter are customarily taken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause of observed deactivation or instability of these dual-function catalyst when they are used in a hydrocarbon conversion reaction is associated with the formation of coke or carbonaceous materials on the surface of the catalyst during the course of the reaction. More specifically, the conditions utilized in these hydrocarbon conversion processes typically result in the formation of heavy, black, solid or semi-solid carbonaceous material which deposit on the surface of the catalyst and gradually reduce its activity by shielding its active sites from the reactants. Recently, there has been developed a new dualfunction catalytic composite which possesses significantly improved activity, selectivity, and stability characteristics when it is employed in a process for the conversion of hydrocarbons of the type which has heretofore utilized dualfunction catalytic composites such as processes for isomerization, dehydrogenation, hydrogenation, alkylation, transalkylation, dealkylation, cyclization, dehydrocyclization, cracking, hydrocracking, reforming, desulfurization, and the like processes. In particular, it has been determined that a catalyst comprising a combination of a platinum group component, a rhenium component, and a halogen component with a porous carrier material enables the performance of hydrocarbon conversion processes which have traditionally utilized dual-function, platinumcontaining catalysts to be substantially improved. For example, it has been demonstrated that the overall performance characteristics of a reforming process can be sharply improved by the use of this recently developed catalyst. Not unexpectedly, the deactivation of this recently developed dual-function hydrocarbon conversion catalyst occurs in much the same manner as for any other hydrocarbon conversion catalyst having a platinum metal component when it is employed in the hydrocarbon conversion service. Accordingly, the principle mode of deactivation of this recently developed catalyst is the deposition of coke, volatile hydrocarbons, and other carbonaceous material on the surface of the catalyst which eventually cover the catalytically active sites of the catalyst, thereby shielding them from the reactants or blocking access of the reactants to the sites. These deposits cause a gradual decline in activity and selectivity of the catalyst and a gradual loss of its capability to perform its intended function. Depending somewhat on the performance requirements imposed on the process utilizing the catalyt, at some point in time the catalyst becomes so clogged with carbonaceous materials that it either must be regenerated or discarded. Heretofore, substantial difiiculty has been encountered in regenerating this recently developed hydrocarbon conversion catalyst. More specifically, it has been determined that the application of conventional regeneration techniques which have been practiced in the art of regenerating dual-function hydrocarbon conversion catalysts, has not been successful in restoring the initial activity, selectivity, and stability characteristics of the catalyst. Typically, the application of conventional carbon-burning procedures with oxygen-containing gases results in a rengerated catalyst having an extremely low activity and containing a reduced amount of halogen component. Attempts at restoring the initial level of halogen contained in the catalyst by well known halogen adjustment procedures on the regenerated catalyst have not been successful. Accordingly, the problem addressed by the present invention is the regeneration of a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum group component, a rhenium component, and a halogen component with aporous carrier material when the catalyst contains deactivating amounts of carbonaceous materials.

The conception of the present invention was facilitated by my recognition that the adverse effects that have heretofore been commonly encountered in attempts to regenerate the subject catalyst by conventional oxygenburning techniques were caused by a failure to appreciate the acute sensitiveness of this catalyst to loss of combined halogen during the regeneration procedure and the attendant difiiculty of restoring a uniform distribution of the halogen component in the catalyst once a substantial amount of halogen is removed from the catalyst. More specifically, I have determined that the presence of the proper amount of halogen component in the subject catalyst is an essential condition for its possession of superior catalytic properties, and that it is an extremely difficult task to restore a uniform distribution of this halogen component in the catalyst once it has been removed during a conventional regeneration procedure by the stripping effect of the regenerating gases. Recognizing this sensitivity of the catalyst to loss of halogen, the present invention is directed at a method of regeneration which maintains a uniform distribution of a high level of halogen on the catalyst throughout the regeneration procedure. Accordingly, I have now found a specific sequence of interrelated steps which enable the successful regenera tion of this recently-developed high-performance hydrocarbon conversion catalyst, and essential features of my method are: careful control of the temperature throughout the regeneration procedure, presence of Water and halogen or a halogen-containing compound in the gas streams used during the carbon-burning step and oxygentreating steps, maintenance of halogen content of the catalyst at a high level during the entire regeneration procedure, and careful control of the composition of the gas streams used in all steps to insure the absence of detrimental constituents.

It is, therefore, a principal object of the present invention to provide an improved method for regenerating a hydrocarbon conversion catalyst comprising a combination of a platinum component, a rhenium component, and a halogen component with a porous carrier material where the catalyst has been deactivated by contact with a hydrocarbon charge stock at elevated temperatures. A corrolary object is to provide a solution to the problem of regenerating these recently-developed, high-performance catalysts which solution enables the substantial restoration of the activity, selectivity, and stability characteristics of the original catalyst. An overall object is to extend the total catalyst life of these recently-developed catalysts and to obtain more efiicient and effective use of these catalysts during their active life. Another object is to provide a regeneration method which maintains the halogen content of the catalyst at a high level throughout the regeneration procedure.

In brief summary, the present invention is in one broad embodiment, a method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum group component, a rhenium component, and a halogen component with a porous carrier material Where the catalyst has been deactivated by deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature. The first step of the method is the carbon-burning step and it comprises contacting the deactivated catalyst with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of a halogen or a halogen-containing compound and an inert gas at a temperature of about 350 to about 500 C. for a first period suflicient to substantially remove said carbonaceous materials. Following this first step, the catalyst resulting therefrom is subjected to an oxygen-treating step by contacting it with a gaseous mixture consisting essentially of about 0.2 to about 25 mole percent about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of a halogen or halogen-containing compound and an inert gas for a second period of at least about 1 to 5 hours at a temperature of about 400 to about 550 C. Thereafter, oxygen and Water are purged from contact with the resulting catalyst by means of an inert gas stream. In the final step, the resulting catalyst is subjected to contact with a substantially Water-free hydrogen stream at a temperature of about 370 to about 600 C. for a final period of at least about 0.5 to about 5 hours, thereby producing a regenerated hydrocarbon conversion catalyst having activity, selectivity, and stability characteristics comparable to those possessed initially by the fresh catalyst.

In brief summary, a preferred embodiment of the present invention is a method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum component, a rhenium component and a chlorine component with an alumina carrier material, Where the catalyst has been deactivated by deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature. The first step of this preferred embodiment is the carbon-burning step and it involves contacting the deactivated catalyst with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent about 0.2 to about 25 mole percent H O, about 0.0005 to about mole percent of chlorine or a chlorine-containing compound and an inert gas at a temperature of about 350 to about 500 C. for a first period suflicient to substantially remove said carbonaceous materials While at least maintaining the chlorine content of the catalyst at its initial level. Following this step, the catalyst resulting therefrom is subject to contact with agaseous mixture consisting essentially from about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of chlorine or chlorine-containing compound and an inert gas for a second period of at least about 0.5 to about 5 hours at a temperature of about 500 to about 550 C. In the third step, the catalyst is subjected to contact with another gaseous mixture consisting essentially of about 0.2 to about 25 mole percent 0 about 0.02 to about 25 percent H 0, and about 0.0005 to about 5 mole percent of chlorine or a chlorine-containing compound and an inert gas for a third period of at least about 1 to 5 hours at a temperature of about 500 to about 550 C. Thereafter, oxygen and water are purged from contact with the catalyst with an inert gas stream. In the final step the catalyst is subjected to contact with a substantially water-free hydrogen stream at a temperature of at least about 0.5 to about 5 hours to produce a regenerated hydrocarbon conversion catalyst having activity, selectivity, and stability characteristics comparable to those possessed initially by the fresh catalyst.

In a more specific preferred embodiment, the present invention is a regeneration procedure, as summarized in the preferred embodiment above wherein the catalyst resulting from the third step is treated with a gaseous mixture comprising about 1 to 30 mile perment H O, about 0.01 to about 1.5 mole percent of chlorine or chlorinecontaining compound and air for a fifth period of at least about 3 to 5 hours at a temperature of about 500 to 550 C. Thereafter, in this embodiment the oxygen and water are purged from contact with this catalyst, and the purged catalyst subjected to contact with a hydrogen stream as described above in the preferred embodiment.

Other objects and embodiments of the present invention encompass further details about the deactivated catalysts that can be regenerated thereby, the conditions and reagents used in each step of the regeneration method, and the mechanics associated with each of these steps. These embodiments and objects will be hereinafter disclosed in the following detailed description of each of the essential and preferred steps of the present invention.

The present invention encompasses a regeneration method which is applicable to a catalyst containing a platinum group component, a rhenium component, and a halogen component combined with a porous carrier material. Although the regeneration procedure is specifically directed to the regeneration of a catalyst containing platinum, it is intended to include within its scope other platinum group metals such as palladium, rhodium, ruthenium,

osmium, and iridium. The platinum group component may be present in the catalyst as the elemental metal or as a suitable compound such as the oxide, sulfide, etc., although it is generally preferred that it be used in the reduced state. Generally, the amount of the platinum group metallic component present in the deactivated catalyst is small compared to the quantities of the other components combined therewith. In fact, the platinum group metallic component preferably comprises about 0.01 to about 1 wt. percent of the deactivated catalytic composite calculated on a carbonaceous material-free and elemental basis. Excellent results are obtained When the catalyst contains about 0.1 to about 0.9 wt. percent of the platinum group metal on the same basis.

Another essential constituent of the catalyst regenerated by the method of the present invention is the rhenium component. This component may be present as an elemental metal or as a chemical compound such as the oxide, sulfide, halide, or in a physical or chemical association with the carrier material and/or other components of the catalyst. Generally, the rhenium component is utilized in an amount sufficient to result in the deactivated catalytic composite containing about 0.01 to about 1 wt. percent rhenium, calculated on a carbonceous material-free and elemental basis. The rhenium component may be incorporated in the catalytic composite in any simple manner and in any stage of the preparation of the catalyst. The preferred procedure for incorporating the rhenium component involves the impregnation of the carrier material either before, during, or after the other components referred to herein are added. The impregnation solution is generally an aqueous solution of a suitable rhenium salt such as ammonium perrhenate, sodium perrhenate, potassium perrhenate, and the like salts. However, the preferred impregnation solution is an aqueous solution of perhenic acid. In general, the carrier material can be impregnated with the rhenium component either prior to, simultaneously with, or after the platinum group metallic component is added to the carrier. However, best results are achieved when the rhenium compound is impregnated simultaneously with the platinum group metallic component. In fact, a preferred impregnation solution contains chloroplatinic acid, hydrogen chloride, and perrhenic acid.

Another component of the catalyst treated by the method of the present invention is a halogen component. Although the precise form of the chemistry of the association of the halogen component with the carrier material is not entirely known, it is customary in the art to refer to the halogen component as being combined with the carrier material or with the other ingredients of the catalyst. This combined halogen may be either chlorine, fluorine, iodine, bromine, or mixtures thereof. Of these, chlorine and fluorine are preferred, with the best results obtained with chlorine. The halogen may be added to the carrier material in any suitable manner either during preparation of the support or before or after the addition of the platinum metal and rhenium components. The halogen component is typically combined with the carrier material in amounts sufficient to result in the deactivated catalyst containing about .1 to about 1.5 wt. percent halogen and preferably about 0.7 to about 1.2 wt. percent halogen, calculated on a carbonaceous material-free basis.

As indicated above, the catalyst that is regenerated by the method of the present invention contains a porous carrier material. Although any porous, refractory carrier material known to those skilled in this art may be used, the preferred material is a refractory inorganic oxide and, more specifically, alumina. This preferred alumina material is typically a porous absorptive, high surface area support having a surface area of about 25 to about 500 or more m. g. Suitable alumina materials are the crystalline aluminas known as gamma-, eta-, and thetaalumina, with gammaor eta-alumina giving best results. In addition, in some embodiments the alumina carrier material may contain minor proportions of other well known refractory inorganic oxides such as silica, zirconia, magnesia, etc. However, the preferred carrier material consists essentially of gammaor eta-alumina; in fact, an especially preferred alumina carrier material has an apparent bulk density of about 0.3 g./cc. to about 0.7 g./cc. and surface area characteristics such that the average pore diameter is about 20 to about 300 angstroms, pore volume is about 0.1 to about 1 ml./g. and the surface area is about 100 to about 500 m. g. An exemplary procedure for preparing a preferred alumina carrier material comprising spherical particles is given in the teachings of U.S. Pat. 2,620,314.

After impregnation of the catalytic components into the porous carrier material, the resulting composite is, in the preferred method of preparing this type of catalyst, typically subjected to a conventional drying step at a temperature of about 200 F. to about 600 F. for a period of about 1 to 24 hours. Thereafter, the dried composite is typically calcined at a temperature of about 700 F. to about 1100 F. in an air stream for a period of about 0.5 to hours. Moreover, conventional pre-reduction and presulfiding treatments are typically performed in the preparation of catalytic composites which are regenerated by the method of the present invention. In fact, it is preferred to incorporate about 0.01 to about 0.5 wt. percent of sulfur component into the subject catalyst by a conventional presulfiding step.

In a preferred embodiment, the catalyst regenerated by the present invention is a combination of a platinum component, a chlorine component, and a rhenium component with an alumina carrier material. These components are preferably present in amounts sufiicient to result in the catalyst containing, on a carbonaceous material-free and elemental basis, about 0.7 to 1.2 wt. percent chlorine, about 0.01 to about 1 wt. percent platinum, and about 0.01 to about 1 Wt. percent rhenium.

As indicated hereinbefore, the principal utility for this type of catalyst is in a hydrocarbon conversion process wherein a dual-function hydrocarbon conversion catalyst having a hydrogenation-dehydrogenation function and an acid-acting function has been traditionally used; for example, these catalysts are used in a reforming process, with excellent results. In a typical reforming process, a hydrocarbon charge stock boiling in the gasoline range and hydrogen are contacted with' the catalyst of the type described above in a conversion zone at reforming conditions. The hydrocarbon charge stock will typically comprise hydrocarbon fractions containing naphthenes and paralfins that boil within the gasoline range. The preferred class of charge stocks include straight run gasolines, natural gasolines, synthetic gasolines, etc. The gasoline charge may be a full boiling range gasoline having an initial boiling point of about 50 to about 150 F., and an end boiling point within the range of about 325 to 425 F., or it may be a selective fraction thereof which generally will be a higher boiling fraction commonly referred to as a heavy naphtha-for example, a naphtha boiling in the range of C to 400 F. provides an excellent charge stock. In general, the conditions used in the reforming process are: a pressure of about 0 to about 1000 p.s.i.g. with the preferred pressure being 100 to about 600 p.s.i.g., a temperature of about 800 to about 1100 F. and preferably about 900 to about 1050 F., a hydrogen to hydrocarbon mole ratio of about 1 to about moles of H per mole of hydrocarbon and preferably about 4 to about 10 moles of H per mole of hydrocarbon, and a liquid hourly space velocity (which is defined as the equivalent liquid volume flow rate per hour of the hydrocarbon charge stock divided by the volume of the bed of catalyst particles) of about 0.1 to about 10 hrr with a value in the range of about 1 to about 3 hrf giving best results.

In harmony with my findings on the criticalness of the halogen component to the performance of this catalyst, it is preferred to operate the hydrocarbon conversion process using this catalyst with injection of a halogen or halogen-containing compound into the feed stream thereto in order to maintain the halogen component of the catalyst at a relatively high level. In particular, it is preferred to add about 1 to about 20 wt. p.p.rn., based on the charge stock, of chlorine or chlorine-containing compounds such as the alkyl chlorides to the charge stock to the process either on a continuous or intermittent basis. The exact amount of halogen added to the process in this fashion is usually determined as a function of the amount of water which is continuously entering the conversion zone and numerous techniques are available for developing the proper correlation between water level entering the conversion zone and the precise amount of halogen which must be added to the feed stream in order to maintain the halogen component of the catalyst at the desired level. For a given charge stock and process these correlations are easily developed by experimental methods well known to those skilled in the art. Regardless of how the halogen component of the catalyst is maintained, it is preferred that it be at a relatively high level before the regeneration procedure described herein is commenced. Specifically, the deactivated hydrocarbon conversion catalyst which is subjected to the method of the present invention should contain at least about 0.1 to about 1.5 Wt. percent of the halogen component, calculated on a carbonaceous material-free and an elemental basis, and more particularly, about 0.7 to about 1.2 Wt. percent.

When the catalysts of the type described above are employed in the conversion of hydrocarbons, particularly the reforming process outlined above, the activity, selectivity, and stability of these catalysts are initially quite acceptable. For example, in a reforming process this type of catalyst has several singular advantages, among which are increased C yield, decreased rate of coke laydown on the catalyst, increased hydrogen make, enhanced stability of both C yield and temperature necessary to make octane, and excellent catalyst life before regeneration becomes necessary. However, the gradual accumulation of coke and other deactivating carbonaceous deposits on the catalyst will eventually reduce the activity and selectivity of the process to a level such that regeneration is desirable. Ordinarily, regeneration becomes desirable when about 0.5 to about 15 wt. percent or more of carbonaceous deposits have been formed upon the catalyst.

When the performance of the catalyst has decayed to the point where it is desired to regenerate the catalyst, the introduction of the hydrocarbon charge stock into the convers on zone containing the catalyst is stopped and the conversion zone purged with a suitable gas stream. Thereafter, the regeneration method of the present invention is performed either in situ or the catalyst may be unloaded from the conversion zone and regenerated in an off-line facility.

An essential feature of the present regeneration procedure IS the presence of halogen or a halogen-containing compound in the gaseous mixtures used during the carbon-burning step and the oxygen-treating steps. Although a halogen gas such as chlorine or bromine may be used for this purpose, it is generally more convenient to employ a halogen-containing compound such as an alkylhalide, which upon exposure to the conditions utilized in these steps is decomposed to form the corresponding hydrogen halide. In addition, the hydrogen halide may be used directly; in fact best results are achieved when a hydrogen halide is used directly in the gaseous mixtures. In general, chlorine or chlorine-containing compounds are the preferred additives for use in the present invention, with the other halogens typically giving less satisfactory results. The preferred rnode of operation involves the use of hydrogen chloride in the gas mixtures used in these steps regardless of the halogen component of the catalyst. In fact, as will be shown in the example, an especially preferred procedure involves the injection of an aqueous solution of hydrogen chloride into the gaseous mixture used in carbon-burning and oxygen-treating steps.

The mole ratio of H to MCI used in the gaseous mixtures employed in these steps in the preferred procedure will range from about 20:1 to about 1000: l, with a mole ratio of about 50:1 to 60:1 giving the best results. Operation of the regeneration method in this fashion insures that the halogen component of the catalyst is maintained at about 0.7 to 1.2 wt. percent of the catalyst throughout the regeneration procedure.

It is to be recognized that another essential feature of the subject regeneration method is that the composition of the gas streams used in the various steps thereof are carefully controlled, and the positive requirements for the composition of each of these gas streams are given hereinafter in a manner which excludes the presence of other materials. In particular, it is a critical feature of the present invention that the gas streams used during the carbon-burning step, the oxygen-treating steps, and the optional halogen-adjustment step are substantially free of compounds of sulfurparticularly, oxides of sulfur and H S-and of carbon monoxide. Likewise, it is essential that the hydrogen stream used during the reduction step be substantially free of both water and sulfur compounds such as H 8. It is, therefore, evident that the gas streams used in each of the steps of the present invention may be once-through streams or recycle streams; provided that in this latter case the recycle streams are carefully controlled to insure that the positive limitations given hereinafter on the contents of the various gas streams are satisfied, and are treated by conventional techniques to insure the absence of detrimental constituents therefrom. Furthermore, it is to be noted that the temperatures given hereinafter for each of the steps refer to the temperature of gas stream used therein just before it contacts the catalyst.

According to the present invention, the first essential step of the regeneration procedure is the carbon-burning step and it involves contacting the deactivated catalyst with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of a halogen or a halogen-containing compound and an inert gas such as nitrogen, helium, carbon dioxide, etc., or mixtures of these. In a preferred mode of operation, the gaseous mixture used in this step contains about 0.5 to about 2 mole percent 0 about 0.1 to about 5 mole percent H O about 0.001 to about 0.25 mole percent halogen or halogen-containing compound and an inert gas. The conditions utilized in this step are: a temperature of about 350 to about 500 C., with best results obtained at a temperature of about 375 to about 500 C., a pressure sufficient to maintain the flow of the first gaseous mixture through the zone containing the deactivated catalyst, such as a pressure of about 1 to 35 atmospheres and preferably about 1 to about 7 atmospheres, and a gas hourly space velocity (defined as the volume rate of the flow of the gas steam per hour at standard conditions divided by the volume of the bed of catalyst particles) of about 100 to about 25,000 hr.- with a preferred value of about 100 to about 2,000 hrr- This first step is performed for a first period sufficient to substantially remove carbonaceous materials from the catalyst. In general, depending obviously upon the amount of carbonaceous material present on the catalyst, a first period of about 5 to about 30 or more hours is adequate in most cases, with best results usually obtained in about 20 to 30 or more hours. Ordinarily, this step is terminated when the differential temperature across the zone containing the catalyst is less than zero for a period of about 0.5- to 5 hours.

The second essential step of the present regeneration method is the primary oxygen-treating step and involves subjecting the catalyst resulting from the carbon-burning step, or the optional preliminary oxygen treatment step (explained hereinafter), to contact with a gaseous mixture consisting essentially of about 0.2 to about 25 mole percent 0 about 0.02 to about 25 mole percent H O,

about 0.0005 to about 5 mole percent of a halogen or a halogen-containing compound and an inert gas which is typically nitrogen. The temperature utilized in this step is preferably relatively higher compared to that used in the carbon-burning step, and is selected from the range of about 400 to about 550 C., with best results obtained at higher temperatures of about 500 to about 550 C. The other conditions utilized in this step are preferably the same as used in the carbon-burning step. The duration of this step is at least about 1 to about 5 hours, with excellent results usually obtained in about 1 to about 2 hours. In a preferred mode of operation, the gaseous mixture used in this step contains a relatively higher amount of oxygen than in the carbon-burning step; more specifically it consists essentially of about 4 to about 25 mole percent 0 about 0.1 to about 5 mole percent H O, about 0.001 to about 0.25 mole percent halogen or a halogen-containing compound and an inert gas. In fact, an especially preferred embodiment of this step involves the use of a temperature of about 500 to about 510 C. and a pressure of about 1 to about 7 atm. for a contact time of about 1 to about 2 hours. The function of this oxygen: treating step is to remove trace amounts of carbonaceous materials which were not burned off during the first step and to insure that the metallic components of the catalyst are oxidized to a positive oxidation state; that is to platium oxide and perrhenic oxide.

Although it is not essential, it is preferred to subject the catalyst resulting from the carbon-burning step to a preliminary oxygen treatment step prior to the essential primary oxygen-treating step described above. This preliminary oxygen-treating step essentially involves subjecting the catalyst resulting from the carbon-burning step to a relatively high temperature (i.e. relative to the temperature used in the carbon-burning step) with a relatively small amount of oxygen in order to burn off any remaining carbon on the catalyst and eliminate any possibility of an uncontrollable, catalyst-damaging exothermic reaction during the primary oxygen-treating step. This step essentially involves contacting the catalyst from the carbon-burning step with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of a halogen or a halogen-containing compound and an inert gas, which is typically nitrogen. In general, the preferred mode for changing from the carbon-burning step to the primary oxygentreating step involves a gradual increase in the temperature of the gaseous mixture being charged to the zone containing the catalyst, although in some cases with experience this transition can be a relatively abrupt one. The purpose of this gradual transition is to prevent the development of a substantial temperature rise in the catalyst bed due to incomplete removal of carbonaceous material during the carbon-burning step. This optional step is generally conducted for a period of about 0.5 to 5 hours at a temperature of about 500 to about 550 C. Once again, the other conditions utilized are preferably identical to those given above in the discussion of the carb0n-burning step. Excellent results are obtained in this step when a gaseous mixture, containing about 0.2 to 3 mole percent 0 about 0.11 to about 5 mole percent H 0 and about 0.001 to about 0.25 mole percent halogen or halogen-containing compound, is used for about 1 to 3 hours at a temperature of about 500 to 510 C. and at a pressure of about 1 to about 7 atm. The function of this preliminary oxygen treatment step is essentially to prepare the partially regenerated catalyst for the more severe oxidation conditions which are typically utilized in the primary oxygen-treating step.

Following the primary oxygen-treating step, it is generally preferred, but not essential, to subject the catalyst resulting therefrom to contact with a gaseous mixture comprising about 1 to about 30 mole percent H 0 and about 0.001 to about 1.5 mole percent of a halogen or a halogen-containing compound and air or an inert gas such as nitrogen. An especially preferred mode of operation for this step involves the injection of an aqueous solution of hydrogen chloride into the air stream used in an amount suflicient to result in a gaseous mixture comprising about 1 to 30 mole percent H O, about 0.001 to about 1.5 mole percent HCl and air. This optional halogen-adjustment step is preferably conducted at a temperature of about 400 to about 550 C. for a period of about 1 to about 10 hours, with excellent results obtained in a period of about 3 to 5 hours at a temperature of about 525 C. The purpose of this step is to adjust the halogen content of the catalyst to an equilibrium value of about .1 to about 1.5 wt. percent of the catalyst and preferably about .7 to about 1.2 wt. percent of the regenerated catalyst, calculated on an elemental basis.

Regardless of whether one or more of these optional steps are performed on the catalyst, the resulting catalyst is thereafter purged with nitrogen or another inert gas to displace oxygen and Water therefrom for a period of time which can be easily determined by monitoring the efiiuent gases from the zone containing the catalysts to determine when they are substantially free of oxygen and water. This step is preferably performed at a relatively high temperature; for example, 500 to 600 C.

After this purge step, the final essential step of the present invention is commenced. It involves contacting the resulting catalyst with a substantially water-free hydrogen stream at a temperature of about 370 to about 600 C. for a final period of at least about 0.5 to about 5 hours. The preferred conditions for this step are temperatures of 450 to 600 C. for a period of at least about 0.5 to 2 hours. Once again, the pressure and gaseous rates utilized for this step are preferably identical to those reported in conjunction with the discussion of the carbonburning step. The purpose of this reduction step is to reduce the metallic components essentially to an elemental state and to produce a regenerated catalyst having activity, selectivity, and stability characteristics comparable to those possessed initially by the fresh catalyst.

In many cases, it is advantageous to subject the regenerated catalyst obtained from the reduction step to an additional sulfiding treatment before it is returned to hydrocarbon conversion service. Although any method known to the art for sulfiding a catalyst can be utilized, the preferred procedure involves contacting a suitable sulfide-producing compound with the reduced catalyst at a temperature of about 20 to 550 C. for a period sufficient to incorporate about 0.01 to about 0.5 wt. percent sulfur. The sulfide-producing compound utilized may be selected from the volatile sulfides, the mercaptans, the disulfides and the like compounds; however, best results are ordinarily obtained with hydrogen sulfide. 'Ihe hydrogen sulfide may be utilized by itself or in admixture with a suitable carrier gas such as hydrogen, nitrogen or the like. Good results have been obtained at a temperature of 375 C. and a pressure of 100 p.s.i.g. with a mixture of H2 and H28.

Following this reduction step, or the optional sulfiding step, the hydrocarbon conversion process in which the catalyst is utilized may be restarted by once again charging the hydrocarbon stream in the presence of hydrogen to the zone containing the catalyst at conditions designed to produce the desired product. In the preferred case, this involves re-establishing reforming conditions within the zone containing the catalyst.

The following example is given to illustrate further the regeneration method of the present invention and to indicate the benefits which are realized through the utilization thereof. It is understood that the example is given for the sole purpose of illustration.

EXAMPLE This example demonstrates the benefits associated with the regeneration method of the present invention by contrasting the results obtained in an accelerated reforming stability test with the fresh, undeactivated catalyst and with the regenerated catalyst produced by the present invention.

The catalysts were all manufactured using inch spherical particles of a gamma-alumina carrier material prepared by the method disclosed in US. Pat. No. 2,620,314. The carrier material had an apparent bulk density of about 0.5 g./cc., a pore volume of about 0.4 cc./g., and a surface area of about mF/g.

The spherical particles were then impregnated with a solution containing chloroplatinic acid, hydrogen chloride, and perrhenic acid to amounts sufiicient to result in the :final catalyst containing about 0.2 Wt. percent Pt and about 0.2 wt. percent Re, calculated on an elemental basis, the impregnated spheres were then dried to about 250 F. for about 2 hours, and thereafter subjected to high temperature oxidation treatment with an air stream containing H 0 and HCl for about 3 hours at 975 F.

After this oxidation treatment, the catalyst particles were contacted with a stream of substantially pure hydrogen (containing less than 1 mole ppm. of water) at a temperature of about 1020 F. for about 1 hour. Thereafter, the catalyst particles were presulfided with a mixture of H and H 8 at a temperature of about 1000 F.

An analysis of the fresh catalyst is given in Table I where it is designated as catalyst AF and its composition reported on a wt. percent of element basis. Also shown in Table I is an analysis of the same catalyst after it has been deactivated by the deposition of carbonaceous materials while being used in a reforming process. The deactivated catalyst corresponding to the catalyst AF is designated catalyst AD.

TABLE I.COMPOSITION OF CATALYSTS Weight; percent Catalyst designation Pt Re 01 S C 1 Based on carbon-free catalyst.

Catalyst AD was then regenerated by a sequence of steps which comprise a preferred embodiment of the present invention to yield regenerated catalyst AR. A summary of the conditions and gas streams used in each of the steps are given in Table II. In view of the fact that each of these steps has been previously explained in detail, the description thereof will not be repeated here except to note that step 1 was the carbon-burning step, step 2 was the preliminary oxygen-treat step, step 3 was the primary oxidation step, step 4 was the halogen adjustment step, step 5 the purge step, and step 6 the reduction step.

TABLE IL-SUMMARY OF REGENERATION METHOD Step Composition of gas stream, T., GHSV, P, Time,

N 0. mole percent C. hr. p.s.i.g. hrs.

1 1% O2, 1% Hi0, 0.014% H01 475 310 5 20 and N:

3-- 21% 3% H O, 0.042% HCl 510 300 5 2 4--- 0.3 H01, 18.5 H2O, 17.0% On 525 1, 300 5 4 and Na 6--- Dry Hz 566 300 5 1 The flow scheme utilized in this laboratory scale reforming plant is as follows: (1) the charge stock and hydrogen are commingled, heated to conversion temperature and passed into the reactor; (2) an eflluent stream is withdrawn from the reactor, cooled to about 55 F., and passed to the hydrogen separator wherein a hydrogen-rich gas separates from a hydrocarbon liquid phase; (3) the hydrogen-rich gas phase is withdrawn and a portion of it vented from the system in order to maintain pressure control; another portion is passed through the high surface area sodium dryer, recompressed, and ultimately recycled to the reactor; and (4) the liquid phase from the separator is passed to the debutanizer column wherein light ends are taken overhead and a C reformate recovered as bottoms.

The characteristics of the charge stock used in the accelerated stability test are given in Table III.

TABLE III.ANALYSIS OF HEAVY KUWAIT NAPHTHA The reforming stability test consists of a line-out period followed by six test periods of 24 hours. The conditions utilized in the tests were as follows: a pressure of 100 p.s.i.g., a mole ratio of hydrogen to hydrocarbon of 9:1, a LHSV of 1.5 hr. and a temperature which is continuously adjusted to achieve a target octane of 102 F-l clear for the C reformate.

The results of these comparison tests are given in Table IV in terms of temperature necessary during each period to achieve target octane and the C yield, on a vol. percent of charge basis, recovered during each test period.

TABLE IVCOMPARISON OF FRESH AND REGEN- ERATED CATALYSTS IN REFORMING TEST TABLE IV.-COMPARISON OF FRESH AND BE GENERATED CATALYSTS IN REFORMING TEST Catalyst AF Catalyst .AR"

vol. 0 vol. Period No. T., F. percent 'I., F. percent As previously explained, the temperature required to make octane, at constant conditions for the same charge stock is a good measure of activity of the catalyst. On this basis, it can be determined from Table IV that regenerated catalyst AR required a temperature to make octane which was comparable to that used with the fresh catalyst AF. It is to be noted that the regenerated catalyst is not precisely equivalent to the fresh catalyst: that is, it requires a slightly higher temperature to make octane; but this is generally to be expected for a regenerated catalyst. Of much greater significance is the degree of approach of the regenerated catalyst to fresh catalyst performance, especially in view of the fact that the application of prior art burning techniques to this catalyst produced a regenerated catalyst which was considered to be substantially and permanently deactivated and to be of no further utility for reforming.

Similarly, C yield at octane is a precise indicator of catalyst selectivity for reforming reactions, and by comparing the C yield data given in Table IV for the fresh catalyst with that for the regenerated catalyst, it is manifest that the regenerated catalyst has selectivity characteristics which are comparable to the fresh catalyst.

Insofar as stability is concerned, the rate of change of temperature necessary to make octane and of C yield with time are commonly used to measure this performance characteristic. From Table IV it can be ascertained that the stability characteristics for the fresh catalyst and the regenerated catalyst are comparable.

It is intended to cover by the following claims all changes and modifications of the above disclosure of the present invention that would be self-evident to a man of ordinary skill in the catalyst regeneration art.

I claim as my invention:

1. A method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum group component, a rhenium component and a halogen component with a refractory inorganic oxide porous carrier material, the catalyst having been deactivated by deposition of carbonaceous materials therein during a previous contacting with a hydrocarbon charge stock at an elevated temperature, said method comprising the steps of:

(1) contacting the deactivated catalyst with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of a halogen or a halogen-containing compound and an inert gas at a temperature of about 350 to about 500 C. for a first period suflicient to substantially remove said carbonaceous materials;

(2) subjecting the catalyst resulting from step (1) to contact with a gaseous mixture consisting essentially of about 0.2 to about 25 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of a halogen or a halogen-containing compound and an inert gas for a second period of at least about 1 to 5 hours at a temperature of about 400 to about 550 C.;

(3) purging oxygen and water from contact with the catalyst from step (2) with an inert gas stream; and,

(4) subjecting the catalyst resulting from step (3) to contact with a substantially water-free hydrogen stream at a temperature of about 370 to about 600 C. for a final period of at least about 0.5 to about 5 hours, thereby producing a regenerated hydrocarbon conversion catalyst.

2. A method as defined in claim 1 wherein said platinum group component of said catalyst is platinum or a compound of platinum.

3. A method as defined in claim 1 wherein said platinum group component of said catalyst is palladium or a compound of palladium.

4. A method as defined in claim 1 wherein said halogen component of said catalyst is chlorine or a compound of chlorine.

5. A method as defined in claim 1 wherein said halogen component of said catalyst is fluorine or a compound of fluorine.

6. A method as defined in claim 1 wherein said porous carrier material is alumina.

7. A method as defined in claim 6 wherein said alumina carrier material is gammaor eta-alumina.

8. A method as defined in calim 1 wherein said deactivated catalyst contains, on a carbonaceous materialfree and elemental basis, about 0.1 to about 1.5 wt. percent halogen about 0.01 to about 1 Wt. percent platinum group metal and about 0.01 to about 1 wt. percent rhenium.

9. A method as defined in claim 1 wherein said deactivated catalyst contains, on a carbonaceous material-free 15 basis, about 0.01 to about 0.5 wt. percent of sulfur component.

10. A method as defined in claim 1 wherein said deactivated catalyst comprises a combination of a platinum component, a chlorine component and a rhenium component with an alumina carrier material in amounts sufficient to result in a catalyst containing, on a carbonaceous material-free and elemental basis, about 0.7 to about 1.2 wt. percent chlorine, about 0.01 to about 1 wt. percent platinum and about 0.01 to about 1 wt. percent rhenium. 11. A method as defined in claim 1 wherein the halogen component of the deactivated catalyst is chlorine or a compound of chlorine and the halogen-containing compound contained in the gaseous mixtures used in steps (1) and (2) is hydrogen chloride.

12. A method as defined in claim 1 wherein the gaseous mixture used in step (1) consists essentially of about 0.5 to about 2 mole percent about 0.1 to about 5 mole percent H O about 0.001 to 0.25 mole percent of a halogen or a halogen-containing compound and an inert gas.

13. A method as defined in claim 1 wherein the gaseous mixture used in step (2) consists essentially of about 4 to about 25 mole percent about 0.1 to about mole percent H O, about 0.001 to about 0.25 mole percent of a halogen or a halogen-containing compound and an inert gas.

14. A method as defined in claim 1 wherein step (1) is performed at a temperature of about 375 to about 500 C. and step (2) is performed at a temperature of about 500 to about 550 C.

15. A method as defined in claim 1 wherein step (4) is performed at a temperature of about 450 to about 600 C.

16. A method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum group component, a rhenium component, and a halogen component with a refractory inorganic oxide porous carrier material, the catalyst having been deactivated by deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature, said method comprising a combination of the method defined in claim 1 with the step of sulfiding the catalyst resulting from step (4) by contacting same at a temperature of about 20 to 550 C. with a sulfide-producing compound in an amount sufiicient to result in a regenerated catalyst containing about 0.01 to about 0.5 wt. percent sulfur.

17. A method as defined in claim 16 wherein said sulfide-producing compound is H 8.

18.. A method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum component, a rhenium component and a chlorine component with an alumina carrier material, the catalyst having been deactivated by deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature, said method comprising the steps of:

(1) contacting the deactivated catalyst with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of chlorine or a chlorine-containing compound and an inert gas at a temperature of about 350 to about 500 C. for a first period sufiicient to substantially remove said carbonaceous materials; (2) subjecting the catalyst resulting from step 1) to contact with a gaseous mixture consisting essentially of about 0.2 to about 3 mole percent 0 about 0.02 to about 25 mile percent H O, about 0.0005 to about 5 mole percent of chlorine or a chlorinecontaining compound and an inert gas for a second period of at least about 0.5 to 5 hours at a temperature of about 500 to about 550 C.;

(3) contacting the catalyst resulting from step (2) with a gaseous mixture consisting essentially of about 0.2 to about 25 mole percent 0 about 0.02 to about 25 mole percent H O, about 0.0005 to about 5 mole percent of chlorine or a chlorine-containing compound and an inert gas for a third period of at least about 1 to 5 hours at a temperature of about 500 to about 550 C.;

(4) purging oxygen and water from contact with the catalyst from step (3) with an inert gas stream; and,

(5 subjecting the catalyst resulting from step (4) to contact with a substantially water-free hydrogen stream at a temperature of about 370 to about 600 C. for a final period of at least about 0.5 to about 5 hours, thereby producing a regenerated hydrocarbon catalyst.

19. A method as defined in claim 18 wherein the chlorine-containing compound in the gaseous mixtures used in steps (1), (2), and (3) is hydrogen chloride.

20. A method as defined in claim 19 wherein the ratio of H 0 to HCl contained in the gaseous mixtures used in steps (1), (2), and (3) is selected from the range of about 20:1 to about :1.

21. A method as defined in claim 18 wherein said gaseous mixture used in step (3) contains about 4 to about 25 mole percent oxygen, about 0.1 to about 5 mole percent H 0 and about 0.001 to about 0.25 mole percent of chlorine or a chlorine-containing compound.

22. A method as defined in claim 18 wherein the chlorine component of the catalyst is maintained, throughout the regeneration, at about 0.7 to about 1.2 wt. percent of the catalyst, calculated on a carbonaceous material-free and elemental basis.

23. A method as defined in claim 18 wherein the gaseous mixtures used in steps (1) and (2) contain about 0.5 to about 2 mole percent 0 about 0.1 to about 5 mole percent H 0 and about 0.001 to about 0.25 mole percent chlorine or a chlorine-containing compound.

24. A method as defined in claim 19 wherein the catalyst resulting from step (3) is thereafter treated with a gaseous mixture comprising about 1 to 30 mole percent H O, about 0.001 to about 1.5 mole percent of hydrogen chloride andair for a fourth period of at least about 3 to 5 hours at a temperature of about 500 to 550 C. and thereafter steps (4) and (5) are performed on the result ing treated catalyst.

25. A method for regenerating a deactivated hydrocarbon conversion catalyst comprising a combination of a platinum component, a rhenium component and a chlorine component with an alumina carrier material, the catalyst having been deactivated by deposition of carbonaceous materials thereon during a previous contacting with a hydrocarbon charge stock at an elevated temperature, said method comprising a combination of the method defined in claim 18 with the step of sulfiding the catalyst from step (5) by contacting same at a temperature of about 20 to 550 C. with a sulfide-producing compound in an amount sufiicient to result in a regenerated catalyst containing about 0.01 to about 0.5 wt. percent sulfur.

26. A method as defined in claim 25 wherein said sulfide-producing compound is H 8.

References Cited UNITED STATES PATENTS 3,558,479 1/ 1971 Jacobson et al. 208139 2,916,440 12/1959 Hogin et al 208-140 2,981,694 4/1961 Engel 252415 3,415,737 12/1968 Kluksdahl 208139 3,617,520 11/1971 Kluksdahl 252466 PT FOREIGN PATENTS 1,044,045 1 1/ 1958 Germany 242415 DANIEL F. WYMAN, Primary Examiner P. E. KONOPKA, Assistant Examiner U.S. Cl. X.R. 

